Johnny Vegas and Sian Gibson are returning for the latest murder mystery set around Draper's Tours. This time they're joined by Annette Crosbie, Jason Donovan, Phil Davis, Sally Lindsay, Joanna Page, Ambreen Razia, Jason Forbes, Mike Wozniak and John Macmillan for a story set around a caravan park. We hear from all of the actors below...

Why have the first two films in this series struck such a chord?

Johnny: It's a terrific ensemble every year. It's great writing, but there is also always the buzz of, "Who's in the next one?" It has a very wide appeal as well. It has what I call the "Bingo Factor". If it's discussed at the bingo by your mum and her friends, it's a success. You also know it's a hit when people from all generations stop you in the street to say, "I did like that thing you did." You just have to be sure they haven't confused you with Columbo. I have one of those faces. People ask, "Weren't you in The Rockford Files?" or, "Weren't you three steps behind Cagney and Lacey in the closing credits? Aren't you the Northern version of Harv?"

Sian: The cast draws people in. If I was a viewer, it would certainly draw me in. It's just very easy viewing. I also hope people love the relationship between Terry and Gemma. It's great family viewing as well. It's something you can sit and watch as a family. My mum and aunties love it. It's very rare that you get a comedy which appeals across the generations like this.

Johnny: You come across certain writers and you have faith in their quality control - and Jason Cook is one of those. As a writer, you have to be mindful of trying to extract too much from an idea, but Jason never does that. The most dangerous thing you can ever do as a writer is presume to know what the public who are keeping you in a job want. When you get to the stage where you think you can foist anything on them, you're in trouble. You might be running a fishmonger's and getting up at 4am to get fresh fish for your customers. Then you start to think, "You know what? Fish fingers will do them." When you do that, you will lose custom along the way. Jason would never do that. He maintains a very high quality control, and that's what makes his scripts so brilliant.

Why have viewers warmed so much to the relationship between Terry and Gemma?

Johnny: For a start, Sian is an absolutely brilliant actress - she has impeccable comic timing. Also, we get on so well off-camera, and that plays into what we do on-camera. We are playing it as straight as we can. Terry and Gemma are two normal people in ludicrous situations. We have perfected the bemused look to each other. It's great to feel that we have got that really good on-screen chemistry. It's also very nice when you can give each other notes without someone saying, "How dare you?" It's that classic thing - it's great fun coming in to work with Sian every day.

Sian: It is just such a joy working with Johnny. You know it's going to be four weeks of non-stop laughs. When we first met, we hit it off straight away. We have a great friendship outside of this little world. He is a really good friend, and my scenes with him are so easy. I just love working with him. The fact that Johnny and I have a great relationship translates onto the screen. Working together feels very natural. The beauty of these films is that while everything else is larger-than-life, Johnny and I try to play the truth of the situation. We are the Everymen.

Where do we find Terry and Gemma at the start of Dial M For Middlesbrough?

Sian: In the first film, Terry was trying to win Gemma over. In the second film, it was early days in their relationship. In the third film, they are still together.

Johnny: He's in a very good place. At the end of the first film, he got the girl of his dreams. And at the end of the second film, she's agreed to marry him. Now Terry is making all the wedding plans because he definitely needs it to happen! Gemma wouldn't have a problem with moving on - "I don't want to raise my children to sleep in the back of a bus!"

Is their relationship flagging, then?

Johnny: No, but that is a danger. The hunt for the murderer is a big turn-on for Gemma. She likes to see Terry step to the fore and deal with things. Gemma is happy to throw herself in danger's way.

What does Gemma see in Terry?

Johnny: What women see in me in real life - a project! Terry is the emotional equivalent of an Airfix model - "I'm going to gently dismantle and rebuild you in a way that makes both of us happy." Terry and Gemma's relationship has developed slowly - I don't think Terry would stand a chance at speed dating with Gemma. They have worked together for a long time. She's looking for someone who will really look after her, and when it happens, they know each other inside out. They both have the same sense of humour.

Sian: There is a real common ground between them. They laugh at the same things. They have the same sense of humour and a real understanding of each other. It was a gradual falling in love, but he caught her attention at a time when she needed it. Also, Terry is so loveable. It's easy to see why Gemma would fall for him.

Guest stars... what attracted you to Dial M For Middlesbrough?

John: The script! It was hilarious. That was the first thing that appealed. When I was reading it in a cafe, I found myself laughing out loud repeatedly. I thought, "OK, this very rarely happens. This is genuinely really funny." I'd seen the previous two films which I thought were very good. I also knew that Ed Bye is a great director. So I was delighted when I was offered a part in it. It's been an absolute pleasure to be part of it.

Joanna: I'd seen the previous two films and thought they were brilliant. I thought it would be great fun to be part of it. When they asked me, I thought, "I'd love to be involved." It's been the most fantastic job.

Jason D: I laughed a lot when I read it. I also thought that Darren was a character I could really explore and that there was some great dialogue which I could get my teeth into. I loved the work of the director Ed Bye as well - what a CV he's got! That was really appealing, too. I also watched the first two films and thought they were hilarious. So I was delighted when they asked me to be involved. I really enjoyed the contrast with the character I've just played, The Pharaoh in Joseph And The Amazing Technicolor Dreamcoat. That's what we do in this business. As actors, we are always trying to do different things. So this job sat perfectly with me. I was also attracted by the great cast - they're all terrific actors.

Sally: I'd seen the first two films and thought they were wonderful. It's a great show for UKTV Gold. They're smashing out of the park with this. This is a mixture of Ealing comedy, Amicus horror and Carry On films, all of which I love. It was lovely to get the call.

Phil: It's just really funny. When I read it, it made me chortle a lot. It's an Agatha Christie spoof. In Agatha Christie, it would be set in a country house, but in ours it's set in a caravan park no one can escape from! It's an ensemble piece and a really nice cast. I was very happy to come on board.

Mike: It's a lot of fun. It's a very silly, glorious, gruesome comedy. I adore comedy in all its forms, but like many people, I am also an absolute sucker for the police procedural. When they are put together like this, I love it. Some of my all-time favourite films are the Peter Sellers Pink Panther movies, Police Squad! and Naked Gun. I have dreamt of being part of something like this. So when they asked me, I jumped at it.

Ambreen: It's just a really, really fun Christmas show. It's a family Cluedo crime horror murder mystery thriller comedy. It's also got a fantastic combination of diverse actors. When I was making it, I learnt a lot and I laughed a lot. Being one of the youngest actors on set, it was such an honour to be part of that brilliant ensemble. I also loved working with Ed Bye, who is an incredible director.

Jason F: It's a whodunnit and you don't know whodunnit!

Sally: The script made me laugh out loud, which is very unusual. It's so funny. It has all the best of The League Of Gentlemen and Inside No. 9. Horror and darkness are made light by normalising them. That's where the comedy lies. It's very dark, but very funny in the same breath. I was on holiday when I got the script. My agent said, "Sorry to disturb you on holiday, but I think you should read this." I said, "I can't do it. It starts the day after I land." But as soon as I read it, of course, I said, "I'd love to do it!"

Why are whodunnits so popular?

Phil: We've always loved crime dramas. They are inherently dramatic - who did it and who's going to be next? Most drama shows on TV are to do with crime. What's nice about this is that it's done as a spoof. You have a lot of spoof horror films, but not many spoof crime dramas.

Sally: We love a murder mystery. We are obsessed with Agatha Christie and the idea that the murderer could be anyone. We love guessing. We also love escapism. There is a lot of brilliant, dark drama at the moment, like Line Of Duty. But there is something joyous about a light, really funny whodunnit like Dial M For Middlesbrough.

John: It has something to do with the fact that human beings are problem solvers by nature. We are hardwired to get to the bottom of things. That's why everyone can get into a whodunnit. It's something inherent to us.

Can you please outline your characters for us?

Joanna: Susan says herself that she is odd. She says that when she was young, she was dropped on her head by her mother. She is very simple. She's a chef, and that's her life. But she's also quite mysterious. You don't know whether she's a baddie or a goodie. She is odd, but also rather frightening. I never get to play characters like this. This is the most comfortable costume I've ever worn. The shoes are hideous, but so comfortable. I'm usually in heels. It's nice not have to do anything to be sexy. I can just be normal.

Sally: Evie models herself on Alexis Carrington in Dynasty. She's far too over-dressed and over-made-up. She wears very expensive clothes, which is ridiculous given that she is running a low rent caravan park. She believes she is running a high-end holiday retreat, but there's nothing high-end or holiday about it. She's tight as a clam. She won't spend any money on the caravan park. It's like that scene in Carry On Camping where everyone is charged a pound for everything.

Phil: Jed is the owner of the caravan park and is a very slippery customer. He's happy to rip everyone off. He is overcharging for everything. He affects an air of being sophisticated and urbane, but that is a long way from the truth. For him, the coach is just full of more victims he can make money out of. Then the dead bodies start cropping up, which is not so good for business. Jed is keen to get the dead bodies dealt with very quickly, but circumstances soon take over. There are lots of floods in the area, so the cops can't come out to investigate. They are stuck there wondering who's going to be the next victim. All the people left in the caravan park start to look at each other nervously. They know it's going to be one of them, because no one else is there.

Mike: I play Neil, a conservationist and keen twitcher. Neil is absolutely full of himself and extremely abusive towards his assistant. He is a pillock of the first order. Neil is a terrible bully. He and his assistant are deeply entwined, but the poor woman is so browbeaten. She doesn't even realise what a bully he is. He needs a good talking to!

John: Chad is an American tourist backpacking across Europe. The term I've come up with is that he is an Instagram hippie. He might be the kind of guy who believes in saving the planet, but he will probably take a lot of pictures of himself doing that. He happens to be in the caravan park when the murders start happening. It is traumatic, but Chad is someone who feels that he can grow and learn from this experience. He is also a bit of a thorn in the side of Terry. They are chalk and cheese.

Ambreen: Penny and her boyfriend Phil have won a holiday to this awful caravan park. She is used to five-star hotels and doesn't like this place at all. She is constantly going on at her boyfriend and moaning to him about leaving. He is totally under her thumb. She wears the trousers. She is from Essex. If you think of some of the characters from The Only Way Is Essex, that's what she's like! She's great!

Jason F: Phil is mute.

John, how did you find it doing an American accent?

I've had to do an American accent a lot before in plays. I'm also in a sketch show called Famalam where we are required to play 30 people per episode. That's tremendous fun, and it means that I have got quite good at doing different accents. My American accent also comes from a lifetime of ingesting American sitcoms and popular culture. Do I have a favourite American show? Seeing as we are working on a murder mystery, I love Mindhunter. It's about serial killers. It's terrifying, but gripping.

Why does the caravan park work so well as a setting for Dial M for Middlesbrough?

Phil: Because it's seedy and nothing works. When new guests arrive, Jed tells them, "You're in luck. We have just had the toilets re-sealed and now they work ... Mostly." That setting is very appropriate for the house style.

Have you enjoyed working with Sian and Johnny?

Annette: Definitely. I may not be able to act with Johnny Vegas again. I found it difficult to keep a straight face. So horror being registered became a battle of wills.

Jason D: Absolutely. They're such warm people. Sian has brilliant timing, and Johnny has this wonderfully dry sense of humour. It appears as if they're putting in minimal effort, but that's just a mark of how skilful and how natural they are as performers. A hell of a lot of the comedy comes through Sian and Johnny.

John: They're both brilliant and lovely to work with. They are very generous, warm, helpful, collaborative, playful and inclusive. It also really helps to have the writer Jason Cook on set. It's very handy. Sometimes he will change a line if he thinks of a funnier one. That's so helpful.

Ambreen: Witnessing Sian and Johnny working off each other was astonishing. Because they have worked together for so long, their chemistry is wonderful to watch. Some of the stuff he does is incredible. He never does the same thing twice. You think you know a scene, but he always surprises you by doing something completely different. You don't know what's coming next with him, and that's thrilling. In fact, the improvisation that all the actors brought was very exciting. The director really allowed us to do totally different things. We were playing on this job. Sian is so incredibly professional and very generous. Gemma is the character that everyone can relate to amongst all these mad people. She provides the sanity in the whole show and grounds it.

Joanna and Sally, you have worked with Johnny Vegas before, haven't you?

Sally: I have been working with Johnny for six years, playing his wife in Still Open All Hours. I have just finished the latest series - he thinks I'm stalking him! He thinks I'm following him around - "You again? I have been with you since May. When will it end?" Johnny is a joy to work with. He is very clever and extremely funny. He comes up with ideas on set, and you think, "Why didn't I think of that?"

Joanna: It's fabulous to be working with him again. He just makes you laugh the whole time. He is naturally funny. When you are filming with him, it is hilarious, but he is also a brilliant actor. But you have to try and compose yourself before doing scenes with him because he's so funny! There have been times when I have had to look down and not into the camera because it was so difficult not to laugh. I have a lot of close-ups, so that's been quite challenging!

Have you also enjoyed collaborating with the rest of the cast?

Sally: Absolutely. I've known Sian Gibson for 20 years - she's amazing. Annette Crosbie and Phil Davis are legends, and Jason Donovan is a joy. Everyone is gorgeous. It's lovely to work with such great people. It's been a very soft landing. It's a very happy place to be.

Joanna: It's a wonderful cast. We are all very excited about working with Jason Donovan. My God, I grew up watching him in Neighbours. I was in love with Scott. When I told my mum I was working with him, she was delighted, too. He is one of the most famous people I've worked with. He's very funny. He looks exactly the same as he did when he was on the cover of Smash Hits.

Sian: That's the real reason I did this! Can you believe it? It's Jason Donovan! Who'd have thought it? We're all very starstruck. He's gorgeous. When we were younger, he was a sensation. He was a beautiful, exotic Australian hunk, and now we are all reliving our late teens. I can't get sacked now, but the casting of Jason was meant to be confidential. However, I've been telling all the mums at school about it, and I've never been so popular. I've never had so many text messages from other mums! I have been pretending that I'm really not fazed that it is Jason Donovan and trying to act cool around him. We tried to make his character not look as handsome as he is, but it's not working. Terry says to Gemma, "I've got no chance with him around!"

Annette: It was a lovely production, for all the reasons that I do this job. You become a part of a large family, all doing a job they enjoy, with people they grow to know and admire. That includes the crew, make-up, costume, props, everyone. If it's a comedy, so much the better. Through it all, Sian Gibson kept a serene, happy face, while dealing with shoes that were agony. I miss them all.

Jason F: I've not worked with any of the cast before, except for one brief encounter with Mr Mike Wozniak on the live-comedy circuit. Being mute meant I was mostly a spectator and spent most of my time watching the star-studded cast in awe. Everyone was absolutely hilarious and supremely welcoming. We talked everything from horror stories to ceramics. I've made a lot of new friends.

What do you hope the viewers' response to Dial M For Middlesbrough will be?

Phil: I hope people will be really entertained. I think it will raise lots of laughter. If we achieve that, we will have succeeded. I hope people will all be spilling their tea because they're laughing so much!

Mike: I hope it will appeal to a really wide audience. I remember sitting down with my mother, sister and daughter to watch Peter Sellers as Inspector Clouseau. All the generations were rolling around with laughter. It was such a lovely shared moment. I hope this will have the same effect.

Why does Dial M For Middlesbrough work so well at Christmas?

Ambreen: It's a really fun show for all the family to watch together. It's a murder mystery that keeps you guessing, and it's also a great laugh. I'll watch it with my family at Christmas. You have to watch it with a lot of people and a lot of Celebrations. Every time someone gets murdered, you have to eat a chocolate!

Jason F: The whole family can argue about who they think dunnit.

Johnny: It's event television. Even though everything is multiplatform these days, at Christmas people still gather around the TV and watch things together. This is the ideal show to watch as a family at Christmas.

Sian: It's a brilliant family show. When the first film came out, I showed it to a few friends. I didn't actually think it would be their cup of tea - it's not Breaking Bad. But they all said, "This is perfect Christmas viewing." Christmas is a time when you want to relax and be entertained and watch something funny together. Hopefully people will know they're getting great stuff - and Jason Donovan! Who is not going to turn their telly on for that? I would!

Joanna: It's perfect Christmas viewing. It's fun and exciting and something everyone can sit down and watch together. It's ideal if you want to wind down with a glass of sherry after a hectic Christmas day. I love all the old women's drinks, like snowballs. But my favourite is sherry, which is what Susan would probably drink! There's something in Dial M For Middlesbrough for everyone.

Jason D: It's light-hearted fun and has a very cheeky sense of humour. Like the first two films, which went down extremely well, this is great British telly with a great cast. TV is very big currency here at Christmas, and this will work really well at that time of year.

Phil: Comedy Christmas specials are always a joy. People really enjoy them. You can sit down as a family to watch this. There is nothing there to scare the children. It's great fun family entertainment.

Mike: It's great communal viewing. You can imagine teenagers and granddad and auntie Barbara all finding a particular character they connect with. Christmas is the only time of year where we get that sort of communal viewing. It is not easily achieved, but this manages it really well. It succeeds in bringing all the generations together.

John: It's the kind of thing when I was a kid that everybody would be able to sit down and watch after a big meal. I hope everyone will have a laugh while eating Christmas cake. I will most definitely be doing that!

Sian, would you like to make more films set on a Draper's Tour?

Sian: Absolutely. I would love to do more. I love how every year we get a different cast. That's one of the most exciting things about it - although we do feel traitorous because every year we miss the cast from the year before. We really bond every year. Then, just before the shoot, Johnny and I will say, "Who's in the cast?" and the actors are always great. This year we've got Jason Donovan, for God's sake!